Furnace.



J. THOMSON w. A. J. FITZ GERALD.

' FURNACE.

APPLICATION FILED MAY 13, 1909.

95Q 878 Patented Man 1, 1910.

3 SHEETSSHEET 2.

hlflT TATES PATENT @FFTKCE OHN THOMSON, OF NEW YORK, AND FRANCIS A. J.FITZ GERALD, OF NIAGARA FALLS, NEW YORK,.ASSIGNORS 'lO IMBERT PROCESSCOMPANY, OF NEW YORK, N. Y., A

CORPORATION OF NEW YORK.

FURNACE.

Specification of Letters Patent.

Application filed May 13, 1909.

Patented Mar. 1, 1910 Serial No. 495,585.

To all whom it may concern:

Be it known that we, JOHN THOMSON, a citizen of the United States,-and aresident of the borough of Manhattan of the city of New York, in thecounty and State of New York, and FRANois A. J. FITZGERALD, a subject ofthe King of Great Britain, and a resident of Niagara Falls, in thecounty of Niagara of said State of New York, have invented .certain newand useful Improvements in Furnaces, of which the following is aspecification, reference being had to the accompanying drawings, forminga part hereof. I

The predominant advantages of fuel-fired, revolving, tubular furnaces,especially in ore smelting, have been fully demonstrated in practice,namely: the mixing of the charge, which reduces the time in fusing, theavoidance thereby of over-heating any portion of the smelting chamber,and the increased endurance of the refractories, due to the more uniformtemperature and greater area.

T e present improvements have to do with revo ving furnaces and whilethey are particularly applicable to electric furnaces of this type,there are several features thereof which may be embodied in fuel-firedrevolving furnaces as well.

The objects of the invention may be concisely stated as follows: toapply, in a revolving furnace, a carbon resister capable of beingelectrically heated to a state of incandesthe cotirdinating hearth in aplurality of segments preferably curved to a radius about equal to thediameter of the furnace chamber; to provide convenient and adequatemeans for maintaining the refractories under compression; to mount thestructure on roller wheels in a manner which shall be inexpensive toconstruct and require a minimum of power to operate; and to provide sucha disposal and construction of the foregoing as shall generally adaptthe furnace for metal melting and ore smelting.

in the embodiment of this invention shown in the accompanyin drawings,Figure 1 is a view in central longitudinal section. Fig. 2 is a' view incentral transverse section. Fig- 3 is a view in longitudinal sectionthrough the resister and its terminals, showing a 1nodification,-and,Fig. 4 is a detached front elevation of an electrode connection.

The heads of the revolving furnace are indicated at a and supportedtherein, as a central cylindrical core extending along the axis of thefurnace, is a composite resist-er. In Figs. 1 and 2, the resister isshown as having a cylindrical casing d which incloses carbon as theelectro-resistive element. The material from which this casing is formedmay be any refractory suitable for the temperature desired, but thepreferred com-. pound is carborundum which has been recrystallized. Theprocess of constructing such a casing consists in taking the ordinarycrystals combined with more or less fine powder, heating them in acylinder, and then raising the temperature in the said cylinder to theformation of silicon carbid. In this wise the material is recrystallizedand the resulting product has a very dense structure whose fracture issuggestive of steel. Not only can a casing of'this kind be raised to atemperature of about 3,600 F. without damage, but itis an excellentconductor of heat. Therefore, this particular material is peculiarlyapplicable for the present purpose, in that it possesses adequatestrength to avoid deformation, a sufficient refractorability to meet themajority of metallurgical requirements, and so high a coefiicient ofheat conduction as not to sensibly diminish the thermic efliciency. Thecarbon contained within the cylinder is to be of such form, orcombination of forms, as will give the desired electrical resistivity inany case. Thus, as shown in Figs. 1 and 2, the main central portion isfilled with granular carbon (Z while at and toward each end a series ofthin carbon disks d are interposed. It will be evident that if thecasing were entirely filled with owdered or granular carbon theresistivity would be at a maximum, while with plates of variousthicknesses, or with a combination of plates and granular matter, asshown, the condition may readiiy be made to best fit the availablevoltage.

The carbon terminals p, to avoid excessive heating in the furnace-heads,preferably enter the ends of the resister casing, and the directmounting for these, in the furnace heads, are quarter sections 7), sayof magnesite. End caps p of suitable heat insulating material cover theouter ends of shaft d solid or hollow, supported in requadrants extendthe entire length of th sential to the accurate control of theelectrothe terminal blocks, except where these caps and blocks arebored, as at p to receive the metallic electrodes 37*, over which areapplied the hubbed sleeves p which receive the electric cables 10 Thesemetallic electrodes are preferably tubular and have longitudinal cuts32", whereby they are free to revolve inthe terminals which, however, inconsequence of the outward spring of the electrode-tongues, formed bythe slots, will maintain a good electrical connection, and the heattherefrom will be rapidly radiated to the atmosphere. In order tomaintain a practically constant pressure upon the carbon within theresister casing, which is esthermicy, steel plates or strips 22 areapplied to the furnace heads, acting resiliently against the caps andthence upon the carbon terminals. Thus any change in the volume of theresister carbon will becompensated, either to take up for a diminutionor to yield against extension. To insure effective electrical contact,the terminals may have a series of carbon pins, as p", in their faces,or be formed conical, as p whereby to increase the surface area asbetween the granular carbon and the terminals.

A modified construction of composite resister is shown in Fig. 3. Herethere is a cesses d in the terminals, and strung along this rod are anumber of carbon disks (Z having molded cavities d of various forms,said cavities being filled with granular material. The terminals -may beresiliently pressed against these disks, as in the instance alreadydescribed. lt will be observed that the outer edges of these carbondisks are shown as im inging each upon the other, but they may eseparated to the extent that the granular carbon shall not escape. Asthere is greater length of granular carbon, longitudinally, contiguousto the supporting refractory shaft, the resistance will be greater alongthis zone, and therefore in this form of resiste r it will be hotter atits outer surface than at its center. In other respects its action isanalogous to that of the resister already described except that so higha resistivity, in any given length, cannot be obtained.

The hearth in this furnace is formed in four quadrants Z of therefractory bricks 2*, the latter being setinto iron casings, having 45flanges a whose outer extensions are adapted to receive bolts and nuts aThese furnace, the furnace chamber 0 being inclosed by the heads ofwedge-bricks a. At each end of the furnace is a cast iron annulus a inwhose outer peripheries gear teeth are cast and whose inner peripherieshave circular flanges a Each end of the peripheral iron casings'isprovided with a flange a. New, upon assembling the struc ture, the boltsand nuts a will. act to draw the quadrants together radially, whilebolts and nuts a will act to press the brickwork of the quadrantstogether lengthwise Hence, practically all of the material in thefurnace which is subject to temperature stresses may be placed underinitial tension with the result that extreme rigidity and very tightjoints are insured, which are features of the first importance in aheavy revolving structure subjected to high internal temperature. -Theaforesaid circular llangcs a are availed of as tires, acting uponfriction wheels a mounted in brackets to and a pinion or pinions a aresuitably mounted to mesh with the gear teeth in the said annular heads.It will be apparent that with the relatively small diameter of thecircular flanges, or tires, the relatively large diameter of thefriction wheels and the high relation of the pinions to the gears, thefurnace may be revolved with the utmost ease and regularity.

While it would be entirely feasible to form. the quadrants of quartercircles, in cross section producing a circular hearth, the contour hereshown is decidedly preferred, that is in which each hearth-section isthe arc of a circle whose radius is about equal to the longestcross-section diameter of the chamber. The two-fold advantage of thisdesign is that for a given mass in the bath its depth will be less, andthat as the charge, whether this be a bath of metal or crushed ore, mustpass from one hearthsection to another across the 45 i11terscc tion, itis necessarily subjected to an intermixture which is not realizable in acircular hearth.

For charging the furnace, a large tubular opening 9 is built intoone ofthe hearth sections, being closed with a refractory plug held securelyin place by a strap 9 bolted to the casing. 'lhis opening may also beutilized for running off slag or quickly emptying the chamber. One ormore tapholes, as 7' may be provided in either or both heads.

The construction, as herein described, involves practically nomachining. The resister and the furnace hearth have a maximum ofendurance, but whenever necessary to substitute a resister, or to repairor renew the hearth, the entire structure, or any essential portion ofit, may be quickly removed and replaced. The thermal efficiency ishighin that while all surfaces of the furnace chamber receive theuniversally radiated heat from the resister, yet all of the hearthsections and a major portion of the heads act as temporary reservoirs ofheat units which are absorbed by the relatively colder charge upon eachrevolution of the furnace.

\Ve claim as our invention:

1. A revolving electric furnace having a carbon resister as a centralcore.

A revolving electric furnace having a cylindrical core containing theelements of the resister.

3. A revolving electric furnace having a carbon resister as a centralcore and its hearth formed in segments.

4. A revolving electric furnace having a cylindrical core containing theelements of the resister, and its hearth formed'in four separablequadrants each extending the entire length of the furnace and beingcurved to a radius about equal to the diameter of the furnace chamber. v

In a revolving furnace the combination with the heads thereof, of asegmental casing, means toform the hearth of the furnace, and fasteningmeans to unite the segments of the casing together and to the heads,said fastening means being adapted to place the hearth" forming meansunder initial tension.

6. In a. revolving furnace, the combination with the heads thereof, of ahearth formed segmentally of refractory bricks, a peripheral casinghaving a corresponding num ber of segments, and means to bolt thesegments of the casing together and to the:

heads, the relation of heads, bricks and casing being such that thebolting is adapted to place the bricks under initial tension.

7. In a revolving furnace,'the combination of refractory bricksconstituting the hearth, a peripheral casing, and an annulus at each endof the furnace bolted to the casing, the bolting being adapted to placethe bricks under an inltial tension lengthwise ofthe furnace.

8. In a revolving furnace, an annulus at periphery, wheels upon whichthe flanges travel, and driving gears meshing with the teeth.

, of a peripheral casing, an annulus at each end thereof, bolted theretoand having an outwardly projecting flange upon its inner periphery andgear teeth in its outer periphery, relatively large friction wheels uponwhich the flanges travel, and relatively small gear wheels engagingtheteeth.

10. In a revolving electric furnace, a single central core comprising arefractory periphery and an electrically resistive filling.

11. In a revolving electric furnace, the combination 'of a singlecentral core, and eleztric terminals entering the core at each en 12. Ina revolving electric furnace, the combination of a single central corecomprising a refractory'periphery and an electrically resistive filling,and electric terminals entering said periphery at each end.

13. In a revolving electric furnace, the combination of a cylindricalcore, electric terminals entering the core at each end, and resilientelectrodes entering said terminals.

IeL'In a revolving electric furnace, the combination of a core, resistermaterial within said core, and means to maintaina constant pressure uponthe resister material.

15. In a revolving electric furnace, the combination of a cylinder core,a carbon filling for the core, terminals at each end of the core, andresilient members to press the terminals against the carbon filling for:the purpose set forth.

. This specification si ed and witnessed this 11th day of-May, D., 1909.

JOHN THOMSON' FRANCIS A. J. FITZ GERALD.

Signed in the presence of G. MCGRANN,

Looms E. VARNEY;

9.- In a revolving furnace, the combination

